How do welding shade numbers add up? Eclipse viewing.

[mike]

I want to look at the eclipse this weekend.
Everybody says a #14 welding shade is good.
I don't have one.

So, how do the numbers stack up when you use 2?
I'm guessing it's not linear, so 7+7 doesn't = 14???

What's the math for stacking welding shades?

Thanks, mike

[Snag]

A much better idea is to punch a pinhole in the center of one end of a
shoebox , and tape a piece of white paper inside the other end . Point the
pinhole end at the sun , there will be an inverted <IIRC> image of the sun
on the paper if you've lined it up properly . Similar in principle to a
pinhole camers , you might google "pinhole eclipse viewer" or similar for
more info .
Welding lenses are not really suitable for viewing the sun , though many
people do it ...;
--
Snag
Learning keeps
you young !

[Existential Angst]

"mike" <spa...@gmail.com> wrote in message
news:jp3dug$pb2$1...@dont-email.me...

More than the dark factor, for eclipses, is the UV factor, and window glass
(and plastic) is fairly opaque to UV.
Beer's law would proly indicate that more lenses would be better for UV than
one dark lens, regardless of the net tinting.
http://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law After all the
bullshit, Absorption is linear with thickness.... LOL

Of course, Snag's advice is always good.
--
EA


>
> Thanks, mike

[Tim Wescott]

If you have a room available that's sunny at the time of day of the
eclipse, cover up the windows and make a pinhole in the shade. You get a
lot bigger solar disk to view, and if you want you can make multiple
holes.

Because you need to make a tradeoff between brightness and focus, you
want a bigger "pinhole": if I recall correctly a 1/16" or even 1/8" is
appropriate for a ten foot distance.

I remember one solar eclipse where, after leaving the building where us
engineering staff had converted a conference room into a solar
observatory, I noticed that the little sun-dapples filtering through the
leaves of the trees were all little solar eclipse pictures.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

[Artemus]

"Existential Angst" <fit...@optonline.net> wrote in message
news:4fb58357$0$14812$607e...@cv.net...

Arc welding puts out lot's of UV. Why wouldn't a helmet already
have UV filters in it?
Art

[Existential Angst]

"Artemus" <bo...@invalid.org> wrote in message
news:jp42u0$86m$1...@dont-email.me...

Even better for eclipses!
--
EA


> Art
>

[DoN. Nichols]

On 2012-05-17, Artemus <bo...@invalid.org> wrote:
>
> "Existential Angst" <fit...@optonline.net> wrote in message
> news:4fb58357$0$14812$607e...@cv.net...
>> "mike" <spa...@gmail.com> wrote in message news:jp3dug$pb2$1...@dont-email.me...
>>>I want to look at the eclipse this weekend.
>>> Everybody says a #14 welding shade is good.
>>> I don't have one.

[ ... ]

> Arc welding puts out lot's of UV. Why wouldn't a helmet already
> have UV filters in it?

It does -- and the auto-darkening ones block the UV even when
they aren't dark.

But -- I suspect that the problem with viewing the sun is more a
matter of IR than UV -- something which can boil the back of your
eyeball. Gas welding glasses have good IR blocking. Arc welding hoods
have good UV blocking. Probably you want both at the same time for
viewing an eclipse -- if you don't go with the pinhole camera approach,
which strikes me as the best -- especially since you can have more than
one person viewing the image at once, instead of fighting over the
filters. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: <BPdnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

[John G]

mike used his keyboard to write :

Try These for a better view.

http://www.sunguntelescope.com/MAIN.html

http://cdn.transitofvenus.org/docs/Build_a_Sun_Funnel.pdf

--
John G

[Steve B]

"mike" <spa...@gmail.com> wrote in message
news:jp3dug$pb2$1...@dont-email.me...

Sent my wife today for two 4 x 5 shade 14 lenses. They said they were out,
and had sold 14,000 lenses. We are SMACK DAB in the middle of the path here
in Toquerville, Utah. My NexGen only goes up to 13. What's up with that?

Steve

[Doug Miller]

Tim Wescott <t...@seemywebsite.com> wrote in
news:gr6dndax_uScGCjS...@web-ster.com:

> I remember one solar eclipse where, after leaving the building where us
> engineering staff had converted a conference room into a solar
> observatory, I noticed that the little sun-dapples filtering through the
> leaves of the trees were all little solar eclipse pictures.

I've seen that before. Way cool, isn't it?

[Bob La Londe]

"mike" <spa...@gmail.com> wrote in message
news:jp3dug$pb2$1...@dont-email.me...

Several years ago (20? 25?) we had something like a 3/4 eclipse. I was
busy working and didn't have much time to play that day, but I sure found it
interesting seeing all the crescent shapes in the shadows when I walked
under a mulberry tree in my back yard. I'ld never heard of such a thing
before. Oh, I knew about pinhole boxes, and my dad had a reflector for
looking at the sun with his telescope, but I never expected to see such a
blatant display of it so casually like that. I wished I had a camera handy
at the time, but I had work to do, and could only enjoy the site for a few
moments.

[anorton]

"mike" <spa...@gmail.com> wrote in message
news:jp3dug$pb2$1...@dont-email.me...

If you convert the shade number (S) into something called "optical density'
(OD), then the OD numbers do add up when you combine them. the formula is:

OD = 0.428 * (S -1)

To convert back from OD to shade # the formula is:

S = 2.33*OD +1

So a shade number of 7 has an OD of 2.568 . Two of these used together have
an OD of 5.136 which is a shade number of 12.96 An OD of 5 or more is
usually considered safe enough for sun viewing.

I have no idea why the welders shade scale was made different than optical
density.

[Randy333]

On Thu, 17 May 2012 18:29:31 -0700, "Steve B" <ste...@gmail.com>
wrote:

Wear sungalsses under the nexgen?

Remove 333 to reply.
Randy

[Artemus]

"anorton" <ano...@removethis.ix.netcom.com> wrote in message
news:aOidnaHaXs8OfyjS...@earthlink.com...

>
> If you convert the shade number (S) into something called "optical density' (OD),
> then the OD numbers do add up when you combine them. the formula is:
>
> OD = 0.428 * (S -1)
>
> To convert back from OD to shade # the formula is:
>
> S = 2.33*OD +1
>
> So a shade number of 7 has an OD of 2.568 . Two of these used together have an OD
> of 5.136 which is a shade number of 12.96 An OD of 5 or more is usually
> considered safe enough for sun viewing.
>
> I have no idea why the welders shade scale was made different than optical density.

Assuming your equations for Shade # vs OD are correct. Then, since
the equations are linear, you can add Shade #'s too by using
S(sum) = S1 + S2 -1.
Art

[anorton]

"Artemus" <bo...@invalid.org> wrote in message

news:jp6e6r$st5$1...@dont-email.me...

You are correct. So I guess that 12.96 number above should really be 13 if
not for rounding errors. By the way, the constants in those equations are
more accurately 3/7 and 7/3.

[Steve B]

"anorton" <ano...@removethis.ix.netcom.com> wrote in message
news:aOidnaHaXs8OfyjS...@earthlink.com...
>

My SIL called, and was in a tizzy because he could not find one shade 14
lens in all of Las Vegas. So, I went to a local eye doctor, and they had a
case of little cardboard glasses for $2 per. My wife musta got the last of
the 14's at the welding shop, as I called there today, and they have a list
of 38 sold if their special shipment comes in before Sunday evening. I am
pretty much at ground zero, about 15 miles south of Kanarraville, the
epicenter of it.

I am going out tomorrow with my 14 lens on my camera, and try out the
settings I googled up, and make a box to shade me somewhat from the sun,
even though I won't be looking at it, I'll be facing it full on for a good
bit. Gonna have a tripod setup.

Gonna be interesting, both the actual event, and the photography. In
Kanarraville, population 456, they estimate 40,000 people will come in for
this event. There is a lot of farm land around there, so guess there will
be room for all. Some of the farmers will probably clean up on renting RV
spots and such. There's a public baseball park, but it won't hold all the
vehicles, rvs, news satellite trucks, etc. They have 50 portapotties. It's
going to be a zoo, and I'm not going near it. I'll watch it from my back
yard.

Steve, xxtreme SW Utah.

[Edward A. Falk]

On related note, I've discovered that my auto-darkening welding
helmet is not triggered by direct sunlight. How can that be?

--
-Ed Falk, fa...@despams.r.us.com
http://thespamdiaries.blogspot.com/

[David Billington]

Edward A. Falk wrote:
> On related note, I've discovered that my auto-darkening welding
> helmet is not triggered by direct sunlight. How can that be?
>
>

Both of mine will intermittently. I have them currently sitting on a
window sill in the kitchen to charge and on a bright clear day when
facing the sun they with darken but not stay darkened. I haven't been
watching them much but just noted that behaviour a few days ago an hour
or two before sun down when the sun was shining directly into that
window. Next good day I'll try and see if they darken in the midday sun.
One will certainly darken when viewing an incandescent bulb up close,
if you remember those, I still have a few. I haven't tried that on the
new one.

[Gunner Asch]

On Thu, 17 May 2012 18:29:31 -0700, "Steve B" <ste...@gmail.com> wrote:

>

Wear a pair of sunglasses and look through the lens.

Bet you wont need the sunglasses though.

Gunner

--
"The danger to America is not Barack Obama but a citizenry
capable of entrusting a man like him with the Presidency.
It will be far easier to limit and undo the follies of an
Obama presidency than to restore the necessary common sense
and good judgment to a depraved electorate willing to have
such a man for their? president.. Blaming the prince of the
fools should not blind anyone to the vast confederacy of
fools that made him their prince".

[Ignoramus28088]

On 2012-05-19, Edward A. Falk <fa...@rahul.net> wrote:
> On related note, I've discovered that my auto-darkening welding
> helmet is not triggered by direct sunlight. How can that be?
>

They are designed for that, it is a feature, not a bug. The idea is to
NOT be triggered by sunlight, but to be triggered by welding
arcs. This is done for weldors who have to work outside.

Just get a old non-electronic helmet to look at the sun.

i

[Jim Wilkins]

"Ignoramus28088" <ignoram...@NOSPAM.28088.invalid> wrote in
message news:QKydndtd2ag27CXS...@giganews.com...

The sensor appears to have a high pass filter so the sun and
AC-powered lights don't trigger it. My Jackson EQ darkens in sunlight
if I wave my hand across it, a quick test to tell if it's turned on.

jsw

[Edward A. Falk]

In article <jp48ll$t9t$1...@speranza.aioe.org>, Steve B <ste...@gmail.com> wrote:
>
>Sent my wife today for two 4 x 5 shade 14 lenses. They said they were out,
>and had sold 14,000 lenses. We are SMACK DAB in the middle of the path here
>in Toquerville, Utah. My NexGen only goes up to 13. What's up with that?

Will your NexGen activate in sunlight? I found that my cheapo mask
will not. Apparently it's designed not to trigger on a steady light
source and there's no manual trigger.

It's all moot now, I suppose, except that the transit of Venus
is coming soon.

[Leon Fisk]

On Wed, 23 May 2012 05:06:22 +0000 (UTC)
fa...@rahul.net (Edward A. Falk) wrote:

>In article <jp48ll$t9t$1...@speranza.aioe.org>, Steve B <ste...@gmail.com> wrote:
>>
>>Sent my wife today for two 4 x 5 shade 14 lenses. They said they were out,
>>and had sold 14,000 lenses. We are SMACK DAB in the middle of the path here
>>in Toquerville, Utah. My NexGen only goes up to 13. What's up with that?
>
>Will your NexGen activate in sunlight? I found that my cheapo mask
>will not. Apparently it's designed not to trigger on a steady light
>source and there's no manual trigger.
>
>It's all moot now, I suppose, except that the transit of Venus
>is coming soon.

Just something to try...

What if you point it at the Sun and then use something like a sparker
(torch lighter, Bic lighter) to trigger it to go dark. Will it stay dark
then, maybe?

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

[Jon Anderson]

I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
catadiptric lens. Only thing I had that would cover that were my gold
coated full face lenses. I did some test shots in my driveway mid-day to
try and get a handle on shutter speeds and such (since the lens is a
fixed f/11), and noticed that after only a few minutes of experimenting
trying to get an idea where I needed to be for the actual event, my
right eye was starting to get that scratchy eyeball feeling most welders
have experienced.

I ended up shooting through a #13, ISO 160, at 1/4000 sec.
Here's 6 of the best:
<http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/>

Obviously late WRT to the eclipse, but for someone wanting to view or
photograph the Venus transit, this might give a clue what you're going
to need to dim the sun enough to see Venus against a full sun. I don't
think a welding lens is going to cut it for the Venus transit. Search
ebay for 'solar filter', there's special films available pretty cheaply
that blocks 99.9999% of visible light.

BTW, a neat tool for photographers, is The Photographer's Ephemeris, a
freebie that integrates with Google Earth data. You can specify a date
and pick a location, it'll show where the sun and moon will rise and
set. You can also use it to determine of there's anything in your line
of sight that will interfere with the shot you wish to compose. (well,
big things like hills...) I used it to make sure I picked a location
where I could get a clear shot at the eclipse. Wouldn't have been able
to shoot it from my driveway due to trees.


Jon

[mike]

Turns out that the weather didn't cooperate.
I found the whole thing very boring. Never found any
images online that showed anything more than a smooth
crescent.
I was expecting some corona or something interesting.

[Leon Fisk]

On Wed, 23 May 2012 11:08:02 -0800
Jon Anderson <jande...@comcast.net> wrote:

<snip>

>I ended up shooting through a #13, ISO 160, at 1/4000 sec.
>Here's 6 of the best:
><http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/>

Nice shots. I used to fool with stuff like this back when I had some
ambition. Film, 35mm stuff that is. I have a couple mediocre digital
cameras but nothing that can use my old 35mm lenses, nor have much
control of the cameras mechanics.

>Obviously late WRT to the eclipse, but for someone wanting to view or
>photograph the Venus transit, this might give a clue what you're going
>to need to dim the sun enough to see Venus against a full sun. I don't
>think a welding lens is going to cut it for the Venus transit. Search
>ebay for 'solar filter', there's special films available pretty cheaply
>that blocks 99.9999% of visible light.

If I really wanted to see this I would get a filter that goes over the
far end of my old Mead 90mm Maksutov-Cassegrain telescope. Like these:

http://www.telescope.com/catalog/search.cmd?form_state=searchForm&keyword=sun+filter

When I was a kid I had an old Tasco refractor telescope (Dad bought it
used for me, a big surprise) that happened to have a Sun filter that
screwed on to the eye pieces. It wasn't much, but if you kept the
magnification within reason and used the Sun filter, you could actually
see sunspots pretty good. I even got to watch a partial eclipse with
it :)

[anorton]

"Jon Anderson" <jande...@comcast.net> wrote in message
news:WH9vr.48138$xK2....@en-nntp-11.dc1.easynews.com...

I think you have definitely shown your welding filter is not flat enough for
full aperture photographic or telescopic use.

This site sells a variety of filter types including just the aluminized
mylar and black plastic sheets.
http://thousandoaksoptical.com/solar.html

[DoN. Nichols]

On 2012-05-23, Jon Anderson <jande...@comcast.net> wrote:
> I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
> catadiptric lens. Only thing I had that would cover that were my gold
> coated full face lenses. I did some test shots in my driveway mid-day to
> try and get a handle on shutter speeds and such (since the lens is a
> fixed f/11), and noticed that after only a few minutes of experimenting
> trying to get an idea where I needed to be for the actual event, my
> right eye was starting to get that scratchy eyeball feeling most welders
> have experienced.

Did you do what is recommended for mirror lenses -- make a cover
for the front, with a small (say 1" diameter) hole off center so your
actual aperture is significantly smaller that f/11. That might have
gotten you down to f/32 or so. One reason for this is to minimize the
heating of the central mirror which can otherwise be damaged by the heat
from all that sunlight. (And it also lets you use a less dense filter
-- you might have been able to get away with a #10 or so.

> I ended up shooting through a #13, ISO 160, at 1/4000 sec.
> Here's 6 of the best:
><http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/>

BTW -- any idea where the multiple rings on the thin side of the
image came from?

> Obviously late WRT to the eclipse, but for someone wanting to view or
> photograph the Venus transit, this might give a clue what you're going
> to need to dim the sun enough to see Venus against a full sun. I don't
> think a welding lens is going to cut it for the Venus transit. Search
> ebay for 'solar filter', there's special films available pretty cheaply
> that blocks 99.9999% of visible light.

And -- use that off center aperture to cut it down even more and
protect the internal parts of the cat lens.

[Jon Anderson]

On 5/23/2012 12:47 PM, anorton wrote:

> I think you have definitely shown your welding filter is not flat enough
> for full aperture photographic or telescopic use.

Me and a few others on the Sony/Minolta forum I frequent. Welding
filters are nowhere near optically clear enough for fine photography!
But it was really a last minute decision I made to just go see what I
could do with this lens. I bought it at a yard sale last year and it's
just sat. Got some real magnification, and in one or two, one can barely
resolve mountains on the left side of the moon.

I tried a shot at home the next day, same exact setup sans the filter.
I'm shooting on a high end Berlebach tripod, hanging a big weight off
the column, mirror lockup, remote trigger. Shot the top of a pine tree
that on Google Earth, looks to be about 1/4 mine away. I can count the
individual pine needles, but even with Photoshop sharpening, it's a bit
fuzzy. Since buying that 800mm, I've found I really like macro and wide
angle stuff, so decided last night to see if I can't trade/sell it and
get an 8-10mm ultra wide angle.

I did just order today some Baader solar film to make a proper filter,
going to try to shoot the Venus transit with my best 200mm.


Jon

[Jon Anderson]

On 5/23/2012 1:56 PM, DoN. Nichols wrote:

> Did you do what is recommended for mirror lenses -- make a cover
> for the front, with a small (say 1" diameter) hole off center so your
> actual aperture is significantly smaller that f/11. That might have
> gotten you down to f/32 or so. One reason for this is to minimize the
> heating of the central mirror which can otherwise be damaged by the heat
> from all that sunlight. (And it also lets you use a less dense filter
> -- you might have been able to get away with a #10 or so.

I did zero research on the specifics of using this type of lens for
solar photography, only looked into filters and saw some folks were
using #13-#14 welding filters.

> BTW -- any idea where the multiple rings on the thin side of the
> image came from?

I am not sure, might be an artifact of the design, or perhaps light
reflecting off the back of the welding lens? I know this type of lens
does strange things with out of focus highlights, one gets little rings
of light instead of smooth bokeh. I bought the lens because the price
was certainly right. I saw a couple listed on ebay shortly after I got
it, for over a grand, though in the month I watched them, they didn't
sell. It's a great lens in the right application, but I'm going to
sell/swap it and for an ultra wide angle.

> And -- use that off center aperture to cut it down even more and
> protect the internal parts of the cat lens.

My main concern and focus on research, was possibly damaging the sensor,
and that sure is an issue w/digital. (hmm, wonder how the folks I saw
driving by one park, fared with their little pocket digital cameras...)
The lens came through it just fine. I've decided if/when I really want
to do astro photography, I'll pick my brother's brain and scope out his rig.

One thing about the Perkin-Elmer lens, is the optics consist of one
solid piece of glass, hence it's name, the Solid Cat. Not sure what
might damage it, unless excess heat on the secondary mirror could damage
the coating. But it survived!


Jon

[Edward A. Falk]

In article <jpj7ok$fif$2...@dont-email.me>,

Leon Fisk <lf...@no.spam.iserv.net> wrote:
>
>Just something to try...
>
>What if you point it at the Sun and then use something like a sparker
>(torch lighter, Bic lighter) to trigger it to go dark. Will it stay dark
>then, maybe?

Actually, simply waving my hand in front the the sensor was enough to get
it to trigger, but as soon as you stop waving, it goes transparent again.

Tried to think of some flickering light source I could use that I would
trust my vision to, and decided it wasn't a good idea.

[Richard Smith]

That's what I've heard - #14 filter. Welding shop volunteered the
story - they sell out whenever there's an eclipse or something like
that. Lots of non-welding types come by the welding supplies shop.
That was near Cambridge, UK. What with the University, there's a lot
of scientific types around.
RS

[Leon Fisk]

On Thu, 24 May 2012 02:53:05 +0000 (UTC)

fa...@rahul.net (Edward A. Falk) wrote:

<snip>

>Actually, simply waving my hand in front the the sensor was enough to get
>it to trigger, but as soon as you stop waving, it goes transparent again.
>
>Tried to think of some flickering light source I could use that I would
>trust my vision to, and decided it wasn't a good idea.

Suspected as much, my idea/thought was too obvious...

I agree on not trusting it to stay dark. If you really have a
hankering to look at the sun and a few bucks to burn, look into getting
a filter that goes over the far end of a telescope. Something like I put
in a link to earlier in my response to Jon. For viewing the sun even a
moderate spotting scope would work fine with one of those filters. Just
being able to see sun-spots in real-time is interesting.

[DoN. Nichols]

On 2012-05-24, Jon Anderson <jande...@comcast.net> wrote:
> On 5/23/2012 1:56 PM, DoN. Nichols wrote:
>
>> Did you do what is recommended for mirror lenses -- make a cover
>> for the front, with a small (say 1" diameter) hole off center so your
>> actual aperture is significantly smaller that f/11. That might have

[ ... ]

>> BTW -- any idea where the multiple rings on the thin side of the
>> image came from?
>
> I am not sure, might be an artifact of the design, or perhaps light
> reflecting off the back of the welding lens? I know this type of lens
> does strange things with out of focus highlights, one gets little rings
> of light instead of smooth bokeh.

Right -- donut bokeh because of the missing part from the
center.

> I bought the lens because the price
> was certainly right. I saw a couple listed on ebay shortly after I got
> it, for over a grand, though in the month I watched them, they didn't
> sell. It's a great lens in the right application, but I'm going to
> sell/swap it and for an ultra wide angle.

Hmm ... it might be multiple reflections from the front surface
of the lens and the rear surface of the filter. Or -- if the filter is
multiple layers, and they were not parallel you would get multiple
reflections from that.

[ ... ]

> One thing about the Perkin-Elmer lens, is the optics consist of one
> solid piece of glass, hence it's name, the Solid Cat. Not sure what
> might damage it, unless excess heat on the secondary mirror could damage
> the coating. But it survived!

I think that it would be that the heat would soften the typical
adhesives used to attach the center secondary mirror to the back of the
lens. In your case, it appears to have been vacuum evaporated onto the
back, so there is no problem.

BTW You are thinking of parting with the lens you said? What lens
mount? And what are you asking for it?

[DoN. Nichols]

On 2012-05-24, Edward A. Falk <fa...@rahul.net> wrote:
> In article <jpj7ok$fif$2...@dont-email.me>,
> Leon Fisk <lf...@no.spam.iserv.net> wrote:
>>
>>Just something to try...
>>
>>What if you point it at the Sun and then use something like a sparker
>>(torch lighter, Bic lighter) to trigger it to go dark. Will it stay dark
>>then, maybe?
>
> Actually, simply waving my hand in front the the sensor was enough to get
> it to trigger, but as soon as you stop waving, it goes transparent again.
>
> Tried to think of some flickering light source I could use that I would
> trust my vision to, and decided it wasn't a good idea.

Stick a small electric motor and a propeller on the front of the
hood so the propeller interrupts the light to the sensor.

[Jon Anderson]

On 5/25/2012 2:07 PM, DoN. Nichols wrote:

> Hmm ... it might be multiple reflections from the front surface
> of the lens and the rear surface of the filter. Or -- if the filter is
> multiple layers, and they were not parallel you would get multiple
> reflections from that.

Used good old duct tape to hold the welding filter to the lens. In
retrospect, I noticed it had shifted a bit as my set progressed, and
wasn't tight against the hood at the end. That could well account for
the multiple reflections.

As to selling, I'll PM that discussion.

Got my Baader solar filter film today, going to machine up a proper
adapter that will thread into my 200mm, insuring it's parallel.


Jon

[DoN. Nichols]

On 2012-05-26, Jon Anderson <jande...@comcast.net> wrote:
> On 5/25/2012 2:07 PM, DoN. Nichols wrote:
>
>> Hmm ... it might be multiple reflections from the front surface

[ ... ]

> Used good old duct tape to hold the welding filter to the lens. In
> retrospect, I noticed it had shifted a bit as my set progressed, and
> wasn't tight against the hood at the end. That could well account for
> the multiple reflections.
>
> As to selling, I'll PM that discussion.

O.K. Beware that my address is "spam-proofed", and the
directions on how to fix it are in my .sig below -- which *may* be
hidden by some setting in your newsreader client.

Also -- any e-mails with large attachments (like photos) just
plain won't make it to me. Filtering done on e-mail size to keep
viruses out of a couple of small mailing lists which I host.

Nothing here yet, so I figured that you should be warned of the
limitations in effect.

Thanks,

[Gunner Asch]

On Wed, 23 May 2012 11:08:02 -0800, Jon Anderson
<jande...@comcast.net> wrote:

>I shot the eclipse with my Sony A700, and a Perkin-Elmer 800mm
>catadiptric lens. Only thing I had that would cover that were my gold
>coated full face lenses. I did some test shots in my driveway mid-day to
>try and get a handle on shutter speeds and such (since the lens is a
>fixed f/11), and noticed that after only a few minutes of experimenting
>trying to get an idea where I needed to be for the actual event, my
>right eye was starting to get that scratchy eyeball feeling most welders
>have experienced.
>
>I ended up shooting through a #13, ISO 160, at 1/4000 sec.
>Here's 6 of the best:
><http://www.flickr.com/photos/10986502@N08/sets/72157629865291990/>

Very nicely done!! I didnt drag out the Cannon A1s, and all I have are
Olympus point and shoots...so my attempts were failures. Shrug

>
>Obviously late WRT to the eclipse, but for someone wanting to view or
>photograph the Venus transit, this might give a clue what you're going
>to need to dim the sun enough to see Venus against a full sun. I don't
>think a welding lens is going to cut it for the Venus transit. Search
>ebay for 'solar filter', there's special films available pretty cheaply
>that blocks 99.9999% of visible light.
>
>BTW, a neat tool for photographers, is The Photographer's Ephemeris, a
>freebie that integrates with Google Earth data. You can specify a date
>and pick a location, it'll show where the sun and moon will rise and
>set. You can also use it to determine of there's anything in your line
>of sight that will interfere with the shot you wish to compose. (well,
>big things like hills...) I used it to make sure I picked a location
>where I could get a clear shot at the eclipse. Wouldn't have been able
>to shoot it from my driveway due to trees.
>
>
>Jon

Thanks!!

[anorton]

"Jon Anderson" <jande...@comcast.net> wrote in message

news:ppYvr.343509$%Q3.1...@en-nntp-15.dc1.easynews.com...

I do not think the apparent multiple images are reflections. I think it is
just due to the waviness of the filter across the aperture. Each image is
formed by a different area of the filter that has a slightly different wedge
angle. The film works because even though it is wavy, the front and back
surfaces remain very parallel and do not deviate the light.

[Jon Anderson]

On 5/26/2012 1:26 PM, anorton wrote:

> I do not think the apparent multiple images are reflections. I think it
> is just due to the waviness of the filter across the aperture. Each
> image is formed by a different area of the filter that has a slightly
> different wedge angle. The film works because even though it is wavy,
> the front and back surfaces remain very parallel and do not deviate the
> light.

What I hadn't noticed, being behind the camera, was that things got warm
enough for the little bits of duct tape to start slipping. By the end of
my shoot, the welding lens was a couple degrees out, far exceeding any
possible waviness in the filter itself.
In any case, a proper machined holder for the Baader filter is still a
nice thing to have and beats the rolled and glued paper tube the
instructions show...


Jon

[anorton]

"Jon Anderson" <jande...@comcast.net> wrote in message

news:hNcwr.58771$xK2....@en-nntp-11.dc1.easynews.com...

But if you you have a flat, parallel piece of glass at an angle in front of
your lens it will not cause any aberration at all for reasonably distant
objects. Even the very dim, double reflection off the inside of the back
surface and then inside of the front surface will overlap perfectly with the
original image for distant objects.

[Jon Anderson]

On 5/26/2012 7:38 PM, anorton wrote:

> But if you you have a flat, parallel piece of glass at an angle in front
> of your lens it will not cause any aberration at all for reasonably
> distant objects. Even the very dim, double reflection off the inside of
> the back surface and then inside of the front surface will overlap
> perfectly with the original image for distant objects.

Ah, ok. Well, the new filter will use in part, a 55mm filter ring to
thread into the the end of the lens. It's the proper filter, it can be
easily stored, and I don't have to worry about it accidentally falling
off while taking pictures, which the taped filter wanted to do. That's
the main reason for machining a proper setup (as well as keeping a touch
of metalwork in the topic <G>). I liked the images I got enough to
invest a bit more time to do it properly in the future.

Jon

[drake...@gmail.com]

On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

Relevant all over again for August 21, 2017.

So based on A Norton's formula:

4 5 6 7 8 9 10 11

4 7 8 9 10 11 12 13 14
5 8 9 10 11 12 13 14 15
6 9 10 11 12 13 14 15 16
7 10 11 12 13 14 15 16 17
8 11 12 13 14 15 16 17 18
9 12 13 14 15 16 17 18 19
10 13 14 15 16 17 18 19 20
11 14 15 16 17 18 19 20 21

So the first column and row are the shades you are adding. Follow 14 on the diagonal to combine your shades. So a #10 + a #5 is #14.
If you want to check the formula the spread sheet link is:

https://docs.google.com/spreadsheets/d/1Tgr6KliJ-01CQit29XhnJTi59sS4DmS6Gxaj_WkMr-8/edit?usp=sharing

[chris...@gmail.com]

This old thread but applies now with 2017 eclipse...

Someone says the numbers DO add up so I figure using two number 10s from cheap Harbor Freight welding goggles will be okay. I wouldn't plan on staring at it for extended periods in any case. Would be cool to put it on front end of telescope and view, but that's pushing it. Long ago I used 6 polarized filters (crossing two at 90 degrees, then three sets at 120 degrees) which made it almost black (easy to see sun) but don't know if it blocks UV and IR. I was stupid (younger..) and used it to look at the sun through a telescope... didn't take long and image got blurry (I don't remember seeing the sun) so looked at filter and it was MELTING... dumb bass... remember burning leaves with sun using mag glass and a telescope is much more powerful... glad I didn't burn my eyeballs (am 60 now so damage from 40 years ago would be apparent).

[Leon Fisk]

They make/sell filters made to go on the end (Objective) of telescopes.
Usually you have to specify a size, like 90mm or 120 mm depending on
your scope. They are for viewing the Sun. Examples:

https://www.amazon.com/Adjustable-Filter-Telescopes-Camera-Lenses/dp/B071FTTVC5/

https://www.amazon.com/Celestron-EclipSmart-Solar-Filter-Telescope/dp/B000YIXRBW/

https://www.amazon.com/Solar-Filter-Unversal-camera-telescope/dp/B071671TC1/

[DoN. Nichols]

On 2017-08-03, chris...@gmail.com <chris...@gmail.com> wrote:
> This old thread but applies now with 2017 eclipse...

> Someone says the numbers DO add up so I figure using two number 10s
> from cheap Harbor Freight welding goggles will be okay. I wouldn't plan
> on staring at it for extended periods in any case. Would be cool to put
> it on front end of telescope and view, but that's pushing it.

With a telescope, the way to go is (assuming that it is on a
tripod) is to mount a white piece of cardboard (or white paper supported
by cardboard) at a proper distance behind the eyepiece, and adjust the
focus so it projects a sharp image onto the cardboard. The more
distant, the larger the image if the focus range is enough.

If the telescope is smaller than the cardboard, put another
piece of cardboard around the back end of the telescope eyepiece, to
make sure that the target cardboard is in the shadow.

If you have a fairly large diameter, mirror lens telescope
(much shorter than the glass refractor only 'scopes for a given power),
you can use a smaller filter mounted off center in some opaque
cardboard, and mount it off center, so it covers the area between the
center mirror mount and the outer rim of the front lens. This reduces
the amount of energy coming through the 'scope, so the filter can be
weaker and smaller than needed for the full aperture of the 'scope.

> Long ago
> I used 6 polarized filters (crossing two at 90 degrees, then three sets
> at 120 degrees) which made it almost black (easy to see sun) but don't
> know if it blocks UV and IR. I was stupid (younger..) and used it to
> look at the sun through a telescope... didn't take long and image got
> blurry (I don't remember seeing the sun) so looked at filter and it was
> MELTING...

*Always* put the filter at the input end of the telescope.

> dumb bass... remember burning leaves with sun using mag glass
> and a telescope is much more powerful... glad I didn't burn my eyeballs
> (am 60 now so damage from 40 years ago would be apparent).

Yes.

Good Luck,

DoN.

--
Remove oil spill source from e-mail

Email: <BPdnic...@d-and-d.com> | (KV4PH) Voice (all times): (703) 938-4564

[David Billington]

My neighbours borrowed a couple of my fixed shade filters when they went
on a cruise in IIRC 2015 for the Norwegian eclipse and they borrowed my
11EW filters and were very happy and many others on the cruise were
envious as the view my neighbours got of the eclipse was apparently far
superior to that through the cruise supplied cheapy filters.

[Martin Eastburn]

That can be done with many small sized optics even a pin hole in a box
to project to the other side.

DO NOT DO THIS through an 8" or larger scope. The optics might shatter.
Those scopes have front of the main optical plane a cover with a
shielded portal. Gold plated as I recall.

I have both 8 and 11" scopes and protect them at all times.

Martin

[Artemus]

"David Billington" <d...@invalid.com> wrote in message news:om0c34$ovl$1...@dont-email.me...

> On 28/07/17 03:21, drake...@gmail.com wrote:
>> On Thursday, May 17, 2012 at 11:53:14 AM UTC-6, mike wrote:
>>> I want to look at the eclipse this weekend.
>>> Everybody says a #14 welding shade is good.
>>> I don't have one.
>>>
>>> So, how do the numbers stack up when you use 2?
>>> I'm guessing it's not linear, so 7+7 doesn't = 14???
>>>
>>> What's the math for stacking welding shades?
>>>
>>> Thanks, mike

5 years ago there was a discussion here on RCM of this very question.
The short answer is S(sum) = S1 + S2 -1.
For full discussion see here:
https://groups.google.com/forum/#!topic/rec.crafts.metalworking/rjyeFrVlxJM
Art
>

[Neon John]

On Thu, 3 Aug 2017 10:18:58 -0700 (PDT), chris...@gmail.com wrote:

>This old thread but applies now with 2017 eclipse...
>
>Someone says the numbers DO add up so I figure using two number 10s
>from cheap Harbor Freight welding goggles will be okay.

they do add but not linearly. The sum is usually one less than the
numerical sum.

I have a wide variety of welding filters here in the lab because of
the wide variety of materials I have to induction heat in a demo,
photograph the heating and send the results to a potential client.

I've built a mechanism to hold a stack of filters in front of my
camera and have installed open source software on the camera to
provide an intervalometer function. The combination of filters that
make both my eyes and my camera happy are a #6 and a #12. According
to a chart I have, that's equivalent to a #15 filter.

Your stack of 2 #10s will probably be too dense, as my chart shows
them to be equivalent to a #18. Especially if you're photographing
the event, you want your camera to be stopped down and timed out
almost completely so that it'll have enough range to see the corona
and solar flares during totality.

Even when just watching, a stack of 2 or 3 filters will be almost
essential. During the last eclipse I used a welding hood with a #13
filter. When totality happened, I flipped up the filter and watched
unfiltered. When that first little bit of the sun shown at the end of
totality, my eyes were instantly dazzled. They teared up and I saw
spots for most of the rest of the event. I wish I'd had a #2 or #3
filter to watch totality with.

While we're on the topic, I'll say something about the cheap cardboard
glasses being sold or given away. I got 2 sets. I drove to my
photographing place, laid down in the back of my truck, put the
glasses on, opened my eyes and... Lasted for about a minute. The
filter is dense enough but the surround is so narrow that glare from
my cheeks reflecting off the back side of the filter dazzled me.

So I've made up a couple of shields out of poster board that will
protect my whole face from the glare.

So any of y'all planning on using those cheap cardboard glasses need
to do a dry run with full sunlight to see if you can stand the glare.

John


John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address

[rangerssuck]

Good point, and I think I'll do just that. This would, I suppose, ba a perfect application for that black gunk football & baseball players smear on their cheekbones.

BTW, Sometimes life is good. We have a business trip scheduled almost a year ago that will have us in Sun Valley Idaho for the eclipse. Woo Hoo!

[hecht....@gmail.com]

Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11. I don't know how the absorption rate increases when stacked. You can buy 4 1/2" by 5 1/4" glass from Air Gas for $3.20. I am have Shade 12 mounted to my binoculars. Everyone else who is poking a hole in a box or black out curtains that is fine. But spend a few pennies and at lease get the paper shade glasses at 7-11 to see the real thing. This is near a once in a lifetime event don't just watch the reflection.

[Ed Huntress]

On Thu, 10 Aug 2017 14:35:38 -0700 (PDT), hecht....@gmail.com
wrote:

>Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11.

NASA says number 14:

"One of the most widely available filters for safe solar viewing is a
number 14 welder's glass, available through welding supply outlets.
More recently, aluminized mylar has become a popular, inexpensive
alternative. Mylar can easily be cut with scissors and adapted to any
kind of box or viewing device. A number of sources for solar filters
are listed below. No filter is safe to use with any optical device
(i.e. - telescope, binoculars, etc.) unless it has been specifically
designed for that purpose."

https://eclipse.gsfc.nasa.gov/SEhelp/safety.html

--
Ed Huntress

[Larry Jaques]

On Thu, 10 Aug 2017 14:35:38 -0700 (PDT), hecht....@gmail.com
wrote:

>Everyone is wasting you time sir. Welding glass is a great was to view the eclipse. Do not go below Shade 11. I don't know how the absorption rate increases when stacked. You can buy 4 1/2" by 5 1/4" glass from Air Gas for $3.20. I am have Shade 12 mounted to my binoculars. Everyone else who is poking a hole in a box or black out curtains that is fine. But spend a few pennies and at lease get the paper shade glasses at 7-11 to see the real thing. This is near a once in a lifetime event don't just watch the reflection.

I wonder how many people you'll blind with that suggestion.
Astronomers and medicos say 14 is the shade, not 11.

-
I am a Transfinancial--A rich person born in a poor person's body.
Please stop the hate by sending me money to resolve my money
identity disorder. --anon

[Richard Smith]

I lived in Cambridge, UK for a while - all the welding suppliers
sell-out of #14's as important solar events came around.
Not tried myself, but #14 is the acknowledged and tested filter.

My thought - 'cos it's glass and thick, you cannot damage it in any
way which compromises its filtration without that being absolutely
obvious by reason of the glass being broken.
Same reason as condom moulds for forming from the natural latex are
made of glass - they are either fully intact or fully broken - nothing
in-between is possible.

[rangerssuck]

On Friday, August 11, 2017 at 2:57:26 AM UTC-4, Richard Smith wrote:

> Same reason as condom moulds for forming from the natural latex are
> made of glass - they are either fully intact or fully broken - nothing
> in-between is possible.

Today, I have learned something new. Thanks, Richard.

[Ed Huntress]

Right! I always wondered why there was no market for condom blowout
patches...

--
Ed Huntress

[SeaSnake]

It's not like you will ever have that problem is it, ya bareback
butthole surfer?

[Martin Eastburn]

Now now Ed That is wishful thinking.

Martin

[Ed Huntress]

On Sat, 12 Aug 2017 22:58:09 -0500, Martin Eastburn
<lion...@consolidated.net> wrote:

>Now now Ed That is wishful thinking.
>
>Martin

I've never minded much being called a cheapskate, but I guess one can
carry it too far...

-
Ed Huntress

[robert...@gmail.com]

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

My welder's supply store stocks #5 and #10. I bought one of each and stacked them and they compare favorably to the #14 i already have. Mathwise, they check out also (OD = 5.564)

[jmah...@fiu.edu]

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

It is not linear 7+7 =/= 14

Simply put S_1 + S_2 - 1 = S_true

Example if you have two shade 7s:
7+7-1=13 Not Safe

[arca...@gmail.com]

On Thursday, May 17, 2012 at 6:29:31 PM UTC-7, Steve B wrote:
> "mike" <spa...@gmail.com> wrote in message
> news:jp3dug$pb2$1...@dont-email.me...

> >I want to look at the eclipse this weekend.
> > Everybody says a #14 welding shade is good.
> > I don't have one.
> >
> > So, how do the numbers stack up when you use 2?
> > I'm guessing it's not linear, so 7+7 doesn't = 14???
> >
> > What's the math for stacking welding shades?
> >

> > Thanks, mike
>

> Sent my wife today for two 4 x 5 shade 14 lenses. They said they were out,
> and had sold 14,000 lenses. We are SMACK DAB in the middle of the path here
> in Toquerville, Utah. My NexGen only goes up to 13. What's up with that?
>
> Steve

The NASA site says that between 12 and 14 is safe but that some find 12 to bright and other 14 to dark but you can't really get 13. There are a lot of "internet experts" who just run with 14 and spout it as gospel.

[smm...@gmail.com]

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:

> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

you can not stack the lens, can still have severe damage, this is coming directly from NASA.

[Larry Jaques]

Direct from NASA, who also gave us Global Warming.

So, you're steering people into buying the cardboard and mylar eclipse
viewing glasses from the Dollar Tree, are ya?

I'll take my chances with indirect viewing, thanks. Having used
pinholes in cards before, I know it works and is detailed. Will try
the binoculars this time, directed onto a card underneath, hopefully
with a larger picture than the pinhole.

[newsr...@gmail.com]

Dear Smm...., what exactly do you mean by "you can not stack the lens"? We're talking about stacking the solar filters, that is, the darkening filters. And, which bit of info exactly "is coming directly from NASA"? Are you employed by NASA? Or are you referring to a document from NASA--if so, would you link to it?

- Neu

[newsr...@gmail.com]

Let's cite sources, and stop speculating re losing eyesight.

By the way, anorton, was your source for the formula SN = 1 + (7/3) OD (stacking welding lenses) this article? http://www.astronexus.com/node/3 Just curious.

NASA & the NSF's AAS: welding shade 12 protects eyesight from the sun.

Aside from relying on stacking welding filter lenses according to a formula to reach Shade #14, notice that the American Astronomical Society features this article (link below) “Solar Eclipse Eye Safety” by Professor B. Ralph Chou, an optometry professor with a degree in astronomy; he's also lead author of the solar viewing standard ISO 12312-2.

On special ISO eclipse glasses vs. welding lens shade 12-14, Chou's article states, "the transmittance requirements specified for welding filters in the standards for occupational eye protection are more stringent than the [solar viewing] ISO 12312-2 standard.”

Chou on shade 12 vs. 14: “The selection of the welding filter shade number is a matter of personal preference in comfort and will depend on atmospheric conditions and personal glare sensitivity. Filters with shade number 12 should be adequate to protect the eyes, but the solar image may be uncomfortably bright. Some observers may find that the solar image viewed through a shade 14 filter is too dim.”

The one welding shop I asked said they did sell shade 13 replacement lenses for welding helmets, but they'd sold out.

But don't believe me until you've read Prof. Chou's “Solar Eclipse Eye Safety” yourself at:
https://eclipse.aas.org/sites/eclipse.aas.org/files/AAS-Chou-Solar-Eclipse-Eye-Safety.pdf

AAS approves shade 12 to 14 here:
https://eclipse.aas.org/eye-safety/iso-certification

NASA approves shade 12 to 14 here:
https://eclipse2017.nasa.gov/safety

They both mention that some people will find shade 14 too dim for viewing the eclipse. And shade 12 too bright, but safe for eyesight.

[Neon John]

On Fri, 18 Aug 2017 10:11:41 -0700, Larry Jaques
<lja...@invalid.diversifycomm.com> wrote:

>On Thu, 17 Aug 2017 12:47:53 -0700 (PDT), smm...@gmail.com wrote:

>>you can not stack the lens, can still have severe damage, this is coming directly from NASA.
>
>Direct from NASA, who also gave us Global Warming.

That's total BS from NASA.

The sun's color temperature after the light has filtered through the
atmosphere is about 5200 deg. My company makes custom induction
heaters. We got a commission to design and build a platinum
reclaiming furnace. Since a BB of platinum is worth about $4000, I
used boiling copper as the substitute during development. Copper
boils at 4644 deg F - very close to the sun's intensity. I used a
welding hood with stacked #8 filters to comfortably observe and
photograph the furnace. Yet the sun, which is just a few hundred
degrees away will somehow commit voodoo on welding filters? BS.

>
>So, you're steering people into buying the cardboard and mylar eclipse
>viewing glasses from the Dollar Tree, are ya?

The ones with both ANSI and UL certification are OK. They're still
uncomfortable to use since the sun's reflection off one's cheeks
reflected off the back side of the glasses causes strong eye strain.

I don't have any of that black makeup that athletes use under their
eyes so strips of black electrical tape will substitute.

Those are for my wife's use. I'll be using my digital welding hood
that goes up to shade #16. Dialed all the way up, the view of the sun
is comfortable and the hood keeps the heat off my face.

So I've read, a welding arc can reach 9000 deg so if the hood with the
proper filters can handle that it can surely handle the sun at half
the brightness.

>
>I'll take my chances with indirect viewing, thanks. Having used
>pinholes in cards before, I know it works and is detailed. Will try
>the binoculars this time, directed onto a card underneath, hopefully
>with a larger picture than the pinhole.

Have you tested that yet on the sun? I wouldn't expect it to work
very well unless you can mount your binocs on a tripod.


I've fabricated a bracket to hold a stack of welding filters in front
of my camera's lens. I've been practicing on the clear sky sun to
determine what combination of filters makes my camera happy.

With full zoom and digital magnification I can see sunspots. I'm
completely satisfied that this setup is safe for my camera and will
yield fairly spectacular shots.

[glachell...@gmail.com]

On Thursday, May 17, 2012 at 12:53:14 PM UTC-5, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

I'm not sure of the shade # but once before during a partial eclipse my brother doubled two shade glasses in a welding helmet and it was perfect. My dad is dead now or I'd ask what his power was in the helmet. He did it for a living so it probably was two #11's.

[Ignoramus30158]

I think that saying "if you look at the sun for a moment, you will go
blind forever" is bullshit. Similar to most anti-Trump bullshit, it is
just ignorant dreck and propaganda.

It is meant to scare people in hopes that this scaremongering would
prevent them from doing truly dangerous stuff, such as staring at sun
for long durations of time. Similar to DARE propaganda and such.

Think about this. When you drive in the morning, evening, or
mountains, you often get sun right in front of your eyes. And you
still keep on driving. Surely, you did not go blind from that.

Similarly, there are many cases when you catch a glimpse of the sun,
say, operating a crane, or doing some outdoor work overhead. I was
craning stuff last week and the sun was right over where the hook
was. It was extremely annoying and I tried very hard to look at it as
little as possible. But still, the sun was right there.

I have no doubt that staring at sun for a long time (more than a
second) would damage your eyes. It is uncomforable enough that people
do not do that.

Now, welding shades are made for professional use to look at powerful
electric arcs right in front of the person. They block most light, UV
and such.

To say that a shade 10 is somehow dangerous, defies common sense.

I have shade 10 welding shades (with gold layer on the outside) and I
tried them to look at the bright sun. They seem to work well, although
the sun appeared to be a bit too bright.

i


i

[tberna...@gmail.com]

So in other words I have to 10 shade so if I tapersonally them together than that should be safe ??

[hspy...@gmail.com]

So I can double up on 2 #11 weld lenses & Im safe?

[Neon John]

On Sun, 20 Aug 2017 12:31:04 -0700 (PDT), hspy...@gmail.com wrote:

>So I can double up on 2 #11 weld lenses & Im safe?

You'll be safe but you probably won't see anything. That would be
equivalent to a shade 21 if they even make them.

For my camera setup, I'm using stacked #12 and #6 filters, equivalent
to a #15. I have the shutter speed set to 1/60 and run aperture
over-ride. As the obscuration progresses, I'm going to remove the #6
filter. As it nears totality, I'll swap the #6 in and #12 out. When
totality is complete, off comes the #6 for a shot or two of totality.
Then I'll reverse the process as the sun becomes un-masked again. All
in an effort to keep the iris from being forced wide open and
therefore underexposing that shot.

I've spent much of the day optimizing the filter vs zoom that gives me
good shake resistance. The Canon's servo controlled moving lens
element for shake reduction does a spectacular job. I got some pix
today where I can clearly make out the texture of the surface of the
sun, see some sun spots and barely see some streamers.

Fingers crossed that tomorrow will be clear.

[Larry Jaques]

On Sun, 20 Aug 2017 16:13:22 -0400, Neon John <n...@never.com> wrote:

>On Sun, 20 Aug 2017 12:31:04 -0700 (PDT), hspy...@gmail.com wrote:
>
>>So I can double up on 2 #11 weld lenses & Im safe?
>
>You'll be safe but you probably won't see anything. That would be
>equivalent to a shade 21 if they even make them.
>
>For my camera setup, I'm using stacked #12 and #6 filters, equivalent
>to a #15. I have the shutter speed set to 1/60 and run aperture
>over-ride. As the obscuration progresses, I'm going to remove the #6
>filter. As it nears totality, I'll swap the #6 in and #12 out. When
>totality is complete, off comes the #6 for a shot or two of totality.
>Then I'll reverse the process as the sun becomes un-masked again. All
>in an effort to keep the iris from being forced wide open and
>therefore underexposing that shot.
>
>I've spent much of the day optimizing the filter vs zoom that gives me
>good shake resistance. The Canon's servo controlled moving lens
>element for shake reduction does a spectacular job. I got some pix
>today where I can clearly make out the texture of the surface of the
>sun, see some sun spots and barely see some streamers.
>
>Fingers crossed that tomorrow will be clear.

I think it was about 10am that the smoke rolled in from a nearby fire
today. Hopefully, the air will remain clear past 9:19am tomorrow.

[maddy...@gmail.com]

Welding glasses shades 13 or higher are completely safe for viewing the sun as they are 99.9% UV-AB protected

[topbuil...@yahoo.com]

On Friday, August 18, 2017 at 8:29:51 PM UTC-5, Neon John wrote:
> On Fri, 18 Aug 2017 10:11:41 -0700, Larry Jaques
> <lja...@invalid.diversifycomm.com> wrote:
>
> >On Thu, 17 Aug 2017 12:47:53 -0700 (PDT), smm...@gmail.com wrote:
>
> >>you can not stack the lens, can still have severe damage, this is coming directly from NASA.
> >
> >Direct from NASA, who also gave us Global Warming.
>
> That's total BS from NASA.

Last time I looked platinum was $1,100 per troy ounce. How many ounces to a BB again?

[bdnor...@gmail.com]

So two #10 lenses together should be fine, correct?

[cor...@gmail.com]

On Thursday, May 17, 2012 at 12:53:14 PM UTC-5, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

I just used 2 number 7 welding shades and everything worked fine. I was also able to take pictures with my S6 Edge. I probably wouldn't use anything less than 2 7's which equates to a number 13 shade.

[timhg...@gmail.com]

On Thursday, May 17, 2012 at 10:53:14 AM UTC-7, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>
> Thanks, mike

I'm reading this and I still don't understand how the Shade numbers were created and calculated. In some posts I see users indicating camera filters such as #13 for used as a neutral density filter to photograph the sun. In this case I can see that a #13 filter is cutting the exposure by 13 stops. Is this, in essence, what the shade filters mean? In other words does a shade 13 filter cut the amount of light passing through from 100% down to .0122% ?
Taking 100% as a starting point and cutting it by 1/2 you obviously get 50%. Given this example when you cut 100% 13 time in a roll you get 0122%
If this is the case then an opacity of 4.00 (as measured on a densitomter) would be enough to block the sun's rays when viewing it.

[Gunner Asch]

There are MANY...many standards...all of which have #13 in them.
Bolts, welding, photography, stamp collecting and so forth.


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[Przemek Klosowski]

On Mon, 21 Aug 2017 15:23:48 -0700, timhguitar wrote:

> On Thursday, May 17, 2012 at 10:53:14 AM UTC-7, mike wrote:
>> I want to look at the eclipse this weekend. Everybody says a #14
>> welding shade is good.
>> I don't have one.
>>
>> So, how do the numbers stack up when you use 2?
>> I'm guessing it's not linear, so 7+7 doesn't = 14???
>>
>> What's the math for stacking welding shades?
>>

I took the numbers from the web and of course like all the other 'gauge'
numbers (wire, sieve, drill, etc), it's a little bit of a dog's
breakfast: you can see the original logic in the trend, but the actual
numbers are all over the place (*). I don't have the data handy right
now, but I remember that a reasonable approximation was

attenuation = (2.6)^(N-1)

where N is the lens' number. To wit, shade #1 is just transparent glass,
shade #2 attenuates 2.6 times, shade #5 is several hundred times down,
and the strongest shade #14 attenuates about quarter million times. The
formula above is accurate to ~10% for most shades, except few where it's
off by a factor of 2 because imperial. This, however, is good enough,
given that eye sensitivity is logarithmic.


(*) check out the plot of drill diameter vs. drill index number: I would
like to know how THAT came about, as the line is all over the place.

[Przemek Klosowski]

On Mon, 21 Aug 2017 09:19:24 -0700, maddy132335 wrote:

> Welding glasses shades 13 or higher are completely safe for viewing the
> sun as they are 99.9% UV-AB protected

Shade #13 has an attenuation of around 100000, so stops 99.999% of all
visible light. The attenuation of UV and IR must be much higher, because
your eye can't even protect itself against the invisible radiation.

[Neon John]

On Sun, 20 Aug 2017 18:39:19 -0700, Larry Jaques
<lja...@invalid.diversifycomm.com> wrote:


>>Fingers crossed that tomorrow will be clear.
>
>I think it was about 10am that the smoke rolled in from a nearby fire
>today. Hopefully, the air will remain clear past 9:19am tomorrow.

We had a few scattered clouds which enhanced the photos. I got some
spectacular shots with my little setup. I'll be posting them at
johndearmond.com toward the end of the week.

[DoN. Nichols]

On 2017-08-22, Przemek Klosowski <prz...@tux.dot.org> wrote:

[ ... ]

> (*) check out the plot of drill diameter vs. drill index number: I would
> like to know how THAT came about, as the line is all over the place.

Well ... start with counting the passes of drawing wire through
reduction dies. (They *are* "wire sized drills" after all.

Then, start moving some sizes a bit to avoid near fractional
sizes. (I think that the only counter-example is #7 = 1/4"). This helps
make a number of sizes between the two series. The next thing is when
metric sizes came into the game so move things a little more to make the
combination of wire sizes, fractional sizes, and metric sizes fill in
most of the gaps in the individual sets. Note that when using roll taps
in imperial sizes, the recommended tap drill is often a metric size.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: <BPdnic...@d-and-d.com> | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

[Jim Wilkins]

"DoN. Nichols" <BPdnic...@d-and-d.com> wrote in message
news:slrnopv4hn.qg...@Katana.d-and-d.com...

> On 2017-08-22, Przemek Klosowski <prz...@tux.dot.org> wrote:
>
> [ ... ]
>
>> (*) check out the plot of drill diameter vs. drill index number: I
>> would
>> like to know how THAT came about, as the line is all over the
>> place.
>
> Well ... start with counting the passes of drawing wire through
> reduction dies. (They *are* "wire sized drills" after all.
>
> Then, start moving some sizes a bit to avoid near fractional
> sizes. (I think that the only counter-example is #7 = 1/4"). This
> helps
> make a number of sizes between the two series. The next thing is
> when
> metric sizes came into the game so move things a little more to make
> the
> combination of wire sizes, fractional sizes, and metric sizes fill
> in
> most of the gaps in the individual sets. Note that when using roll
> taps
> in imperial sizes, the recommended tap drill is often a metric size.
>
> Enjoy,
> DoN.

http://www.harveytool.com/secure/Content/Documents/Tap_Drill_Chart.pdf
-jsw

[timmc...@gmail.com]

On Thursday, May 17, 2012 at 1:53:14 PM UTC-4, mike wrote:
> I want to look at the eclipse this weekend.
> Everybody says a #14 welding shade is good.
> I don't have one.
>
> So, how do the numbers stack up when you use 2?
> I'm guessing it's not linear, so 7+7 doesn't = 14???
>
> What's the math for stacking welding shades?
>

> Thanks, mike

I found a transmittance chart at
https://www.smokstak.com/forum/attachment.php?attachmentid=288881&d=1503068175

The person who posted it said that you take the figure given for the percentage of transmittance from the nominal percentage column for each shade you want to use in your stack and multiply those number to arrive at a figure for the resulting transmittance and find the shade having that number in the range given for that shade between the nominal and minimum columns.

That is not exactly correct. You must divide the percentage figures by 100 before multiplying in order to the the transmittance factor, multiply those and then multiply the result by 100. Take that number and look to see what range it falls into.

The shade being given by NASA as being safe is 14.

You are therefore, looking for two shades (could do three, but will not go there just now) that work out to a combined value of between 0.00027% and 00016% Luminous Transmittance.

If you had two shades of square root (0.00027 / 100) x 100 = 0.1643 %, those together would equal 0.00027% transmittance.

A way of looking at that is that 0.1643 percent of 0.1643 percent is 0.1643 percent times 0.1643/100 = 0.0002699. (rounding affected the figures at little)

The chart shows that two #5 shades have a range including 0.1643.

If you take the nominal figures for two non-identical shades and work them out, you can see what shade number would be comparable.

If you had a #3 at 13.9% transmissivity, you would need #12 at .0019 to get into the range of a #14. That range is from 0.00027 percent up to 0.00016 percent.

0.139 x 0.000019 x 100 = 0.0002641 percent.

Using a #11 with a #3 yields 0.139 x 0.000052 x 100 = 0.0007228 percent, which falls a smidgen above the range of a # 13.

There are gaps in the transmissivity ranges between the shade numbers.

One might assume the Maximum Effective Far-Ultraviolet Average Transmittance figures are also percentages and it might do to verify those figures and see now they work out when stacking.

I followed the advice of the person whose post I saw that included the chart at the above address and ended up with very dark shading, since I did not have a #14.

I am not sure I missed a lot since the difference in the views would be some brightness but no detail would be apparent. Just the clear partial discs.

A proper pin hole viewer would have been better, I expect.

I posted this mainly because I am interested in understanding things and take notice when I see little errors in logic. You can't directly multiply percentages as was in an earlier post.

Otherwise, 5 percent times 5 percent would be 25 percent. In fact, it is 5 x .05 = 0.25 percent.

Tim.